Water arrived on Earth later than previously thought

The formation of Earth and the origins of life on our planet have long been shrouded in mystery, with one of the most enduring questions being when water, a crucial ingredient for life, arrived on the scene. Recent research led by a team of scientists has shed new light on this enigma, suggesting that water-bearing materials did not coalesce on Earth during its early formation stages. Instead, the data indicate that these vital components were delivered to our planet in its later developmental phases, known as late accretion, which occurred after the Moon’s formation.

By analyzing the isotopic composition of molybdenum in meteorites and Earth rocks, the researchers have been able to reconstruct the planet’s history, providing valuable insights into the timing and circumstances under which life-embracing water became an integral part of our terrestrial landscape. This novel understanding has profound implications for our comprehension of the solar system’s evolution and the emergence of life on Earth, highlighting the complex interplay between celestial mechanics, geochemistry, and the primordial conditions that ultimately gave rise to our planet’s unique biosphere.

Introduction to the Origins of Water on Earth

The question of when water arrived on Earth is crucial in understanding the origins of life on our planet. Scientists have long sought to determine the timing of this event, as it is essential for understanding how and when life began. According to current scientific understanding, at least three necessary ingredients are required to kick-start life: water, energy, and a soup of organic chemicals known as CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur). A team of researchers led by Katherine Bermingham, an associate professor in the Department of Earth and Planetary Sciences at Rutgers University, has made significant progress in addressing this question. By studying the isotopes of the element molybdenum, they have concluded that water did not arrive as early during Earth’s formation as previously thought.

The study focused on analyzing the molybdenum isotopic composition of meteorite samples and Earth rocks to gain insights into the events occurring around the time of Earth’s final core formation. This period is thought to coincide with the Moon’s formation, which is believed to have occurred when the last 10% to 20% of material was being assembled by the planet. The researchers extracted molybdenum from meteorite samples obtained from the National Museum of Natural History of the Smithsonian Institution and compared their isotopic composition to that of Earth rocks from various locations around the world. By analyzing these samples, they aimed to determine when water was delivered to Earth and how it relates to the origins of life.

The team’s findings suggest that the Moon-forming event was not a major supplier of water, unlike what has been thought previously. Instead, their data support the interpretation that water was delivered to Earth in smaller portions after the Moon was formed, during a period known as late accretion. This conclusion is based on the similarity between the molybdenum isotopic composition of Earth rocks and meteorites sourced from the inner solar system (NC), rather than those from the outer solar system (CC). The researchers believe that this finding provides valuable information about the origins of water on Earth and the conditions under which life emerged.

Methodology and Sample Analysis

The study employed an observational approach, analyzing the molybdenum isotopic composition of meteorite samples and Earth rocks to draw inferences about the origins of water on Earth. The researchers collected meteorite samples from the NC group, which is characterized by its formation in the inner solar system. They also gathered Earth rocks from various locations, including Greenland, South Africa, Canada, the United States, and Japan, which are thought to have been formed during the time of the Moon’s formation. By comparing the molybdenum isotopic composition of these samples, the team aimed to identify similarities or differences that could provide insights into the origins of water on Earth.

The analysis revealed that the Earth rocks studied were more similar to meteorites sourced from the inner solar system (NC) rather than those from the outer solar system (CC). This similarity suggests that the Earth’s building blocks, including dust and gas, came from the inner solar system. The researchers also found that the molybdenum isotopic composition of the Earth rocks was distinct from that of the meteorites, indicating that the Earth had not received a significant amount of water from the Moon-forming event. Instead, their data support the interpretation that water was delivered to Earth in smaller portions after the Moon was formed, during late accretion.

Implications and Conclusion

The study’s findings have significant implications for our understanding of the origins of water on Earth and the conditions under which life emerged. The conclusion that the Moon-forming event was not a major supplier of water challenges previous theories about the delivery of water to Earth. Instead, the data suggest that water was delivered in smaller portions during late accretion, which may have occurred after the Moon was formed. This finding provides valuable insights into the origins of life on Earth and highlights the importance of continued research into the early history of our planet.

The study’s results also underscore the complexity of the processes involved in forming our solar system and delivering water to Earth. The researchers’ use of molybdenum isotopes as a tracer for the origins of water on Earth demonstrates the power of geochemical analysis in addressing fundamental questions about the history of our planet. As scientists continue to explore the origins of life on Earth, studies like this one will play a crucial role in advancing our understanding of the complex processes that have shaped our planet over billions of years.

The Significance of Late Accretion

The concept of late accretion refers to the process by which small amounts of material, including water, were delivered to Earth after the Moon was formed. This period is thought to have occurred during a time when the solar system was still in its early stages of formation, and the planets were still undergoing significant changes. The study’s findings suggest that late accretion played a crucial role in delivering water to Earth, which is essential for life as we know it.

The significance of late accretion lies in its ability to provide a mechanism for water delivery to Earth without relying on the Moon-forming event. This challenges previous theories about the origins of water on our planet and highlights the complexity of the processes involved in forming our solar system. The study’s results also underscore the importance of continued research into the early history of our planet, including the role of late accretion in shaping the Earth’s surface and creating conditions suitable for life.